Fitness exercise bar systems, such as dumbbells or barbells or curl bars, which use interchangeable weights are well known in the art. A typical system employs an elongate bar or rod, removable hard-surface weights and some mechanism for retaining the weights on the bar.
Most such fitness exercise bar systems retain the interchangeable hard-surface weights on a bar by employing a collar formed as part of, or attached to, the bar and a movable end piece which is removably attached to the bar. In operation, interchangeable weights are slid onto the bar and locked between the moveable endpiece and the collar. In one variation, the bar itself is modified to provide a threaded flange for the moveable endpiece, see, for example, U.S. Pat. No. 4,738,446 to Miles. However, in exercise bar systems of this type, the hard-surface weights are not connected to each other and can rotate and slide horizontally when being used if the interchangeable weights are not tightly clamped between the moveable endpiece and the collar.
Some other types of fitness exercise bar systems use hard-surface weights which attach directly to the each other and to the ends of the bar. U.S. Pat. No. 4,566,690 to Schook ("'690 patent") is an example of this type. In the '690 patent, each weight is formed with a single male connector on one side and a single female connector on the other side. The individual weights can be connected to each other by joining the weights together and to a collar at the end of the bar. However, aligning the centrally located cylindrical connectors without the guidance and support provided by a central bar or additional guides can be difficult. Furthermore, attaching a hard-surface weight to an adjoining hard-surface weight requires that an individual weight be spun about the handle to insure a tight fit between the weights. Also, the '690 patent does not provide any means for "locking" the weights together once the weights are connected to each other.
Another type of fitness exercise bar system attaches each hard-surface weight directly to the handlebar. U.S. Pat. No. 4,453,710 to Plotz ("'710 patent") shows a bar formed with tabs along at least part of the bar. Each weight in the '710 patent has complementary stops formed along the weight's center hole to engage the stops and, when twisted, lock the weight to the handlebar. However, this system requires that weights be positioned only in specific places along the bar, that is, where the tabs are positioned.
Also, in the prior art, weights of different masses typically have different diameters. In these systems, using different weights on each end of the handlebar, for example, a 1 kilogram weight and a 3 kilogram weight on one end and a single 4 kilogram weight on the other end, creates a geometric imbalance, although the total mass, 4 kilograms, is the same.
Therefore, there is a need for a fitness exercise bar system which overcomes the deficiencies of the prior art systems discussed above.